In order to obtain consistent, accurate, and predictable color rendering on display devices, calibration is typically required to adjust certain aspects of a display so that these aspects conform to a particular standard, such as the sRGB (standard Red Green Blue) standard color space. Display devices often allow for the adjustment of the display's brightness, contrast, gamma, and white point or color balance. There are several ways of calibrating the gamma of display devices, which is the name of the nonlinear operation used to code and decode luminance or tristimulus values in video or still image systems. One such way includes the use of measurement instruments, which may include a colorimeter or spectrophotometer. Another such way is to present the user with a visual target image that guides the gamma adjustment. Traditionally, visual target images that have been used for gamma adjustment require the viewer of the display device to squint or use other methods to blur or put the viewer's eyes out of focus to get an accurate adjustment of the gamma. These visual target images are therefore not user friendly, requiring considerable time and effort on the part of the viewer.